Rechargeable Battery Pack and Electrical Hand Tool Device

ABSTRACT

The invention relates to a rechargeable battery pack, in particular for an electrical hand tool device, comprising at least two series-connected rechargeable battery cells ( 20 ) and/or rechargeable batter cell blocks and an electronics unit having a printed circuit board ( 14 ), wherein sheet metal conductors ( 16 ) for electrically connecting the series-connected rechargeable battery cells ( 20 ) and/or rechargeable battery cell blocks are provided, wherein the sheet metal conductors ( 16 ) are connected directly to the printed circuit board ( 14 ).

The invention relates to a rechargeable battery pack, in particular onefor a hand-held power tool, comprising at least two battery cells orbattery cell blocks connected in series and an electronics unit with aprinted circuit board, whereby sheet metal conductors are provided forelectrically connecting the in series connected battery cells or batterycell blocks.

For example, it is often practiced to use battery packs for operatinghand-held power tools because cordless tools offer greater flexibilityduring work and, in particular, independence from an existing powersource, thus allowing work outside to be independent of the requirementsof an electrical power outlet. Cordless tools include a rechargeablebattery in a battery housing that can be coupled with the tool housingof the hand-held power tool, where upon coupling of the two housings themotor is electrically connected to the battery pack and is supplied withelectricity from it. To couple the two housings, the battery housing istypically provided with a protruding locking device that is insertedinto and engages in a complementing socket of the tool housing. Theelectrical contacts are typically established in the area of the lockingdevice.

As a rule, it is provided to connect the individual battery cells, orthe individual battery cell blocks, respectively, in series. At times,so-called sheet metal conductors are used providing the connection ofrespective complementary poles of a battery cell to each other.

A similar design for a battery is, for example, known from DE 94 04070.2 that describes a battery set, where individual batteries arearranged in battery-holding cells, whereby sheet metal conductors areused to provide the series connection of the individual batteries toeach other. Here, the sheet metal conductors are arranged in a curvedmanner according to the description.

In addition, it known for lithium ion batteries where the charge leveland the charging procedure are monitored via the electronics of thebattery pack to provide that the individual battery cells are connectedwith the electronics for the purpose of monitoring their cells. To thisend, the state-of-the-art provides stranded wires that connect thebattery cells with the electronics unit and here in particular with thepc-board. One disadvantage of this is the relatively high cost ofassembly.

It is, therefore, the objective of the invention to provide a batterypack, where the series connections of the battery cells to each other aswell as the connection to the pc-board are simplified.

According to the invention, this is done in that a battery pack of thegeneric kind provides such sheet metal conductors which are connecteddirectly with the pc-board. In this manner, there is no need toadditionally establish contacts between the individual battery cells andthe electronics using stranded wires. It is particularly advantageous ifthe sheet metal conductors are used to establish both an electrical anda mechanical connection between the individual battery cells and thepc-board. In this manner, a support for the pc-board can be achieved bythe sheet metal conductors in relation to a battery cell or a batterycell block at the same time. Here, a battery cell block refers to two ormore battery cells that are switched in parallel and are connected inseries to additional battery cells or battery cells blocks.

It can be provided that the sheet metal conductors are designedgeometrically such that they protrude from the side of the pc-board inthe form of terminal lugs. They can then be angled such that they pointfrom the pc-board in the direction of the battery cells.

It is particularly advantageous if the sheet metal conductors arefastened to the pc-board by rivet joints. Rivet joints provide both avery simple mechanical and electrical contact and great reliability.Finally, using appropriate rivet joints can provide tolerancecompensation as well as thermal expansion compensation.

In general, the mechanical as well as the electrical connection viasheet metal conductors to the pc-board offers the advantage that thepc-board is spring-supported in relation to the battery cells or thebattery cell blocks, respectively, because the sheet metal conductorsalso act as spring elements. This achieves additional vibration strengthbecause especially vibrations that occur with hand-held power tools, inparticular with impact drills or hammer drills, can be compensated.

The combination of these various aspects in one component establishesthe particular advantage of the invention.

In particular, the battery cells can be lithium ion cells. In particularwith lithium ion cells it is possible to combine several battery cellsto so-called battery cell blocks, where several battery cells areconnected in parallel. In this case, one battery cell block each isconnected with the electronics. Using the electronics, among otherthings, the charge level can be monitored via the voltage of theindividual cells. In addition, the charging process can be controlled.The voltage for parallel connected cells is always the same; thus, forbattery cell blocks, the voltage must be determined for each block.

By connecting the battery cells, or the battery cell blocks,respectively, to the pc-board, it can be determined, whether all batterycells are charged properly and/or whether a charging current is reachedthat the battery cells are not able to handle. Furthermore, a controlcan be provided that controls the charge current such that overloadingof individual battery cells is prevented yet all battery cells can becharged fully. This results in a good usability of the respectivebattery pack and thus of the hand-held power tool using the battery packover a long time. The poles of the individual battery cells can have amaterial connection, especially through welding or soldering, to thesheet metal conductors. In addition, it can be provided that the batterycells are supported by a battery cell carrier and are kept at a distancefrom each other in this carrier. This avoids shorts caused by contactbetween the individual battery cells. The cell carrier can be made of aninjection-molded component that exhibits respective receptacles for thebattery cells. Furthermore, fastening elements can be provided at thecell carrier that are used to connect the cell carrier holding thebattery cells, which as a unit are called corepack, with the electronicsunit. A respective connection can be established, for example, via alatch connection, where respective latching devices are provided at thecorepack in which latch protrusions reach behind the electronics unitunder mechanical deformation and in this manner provide a positiveconnection.

In addition to the pc-board, the electronics unit may also include anelectronics housing in which the pc-board with the attached sheet metalconductors can be placed. Finally, the pc-board holds a number of otherelectronics elements and a software for controlling or even forrecognizing the battery pack can be loaded onto the pc-board. Additionalcomponents, in particular switches but also charge level indicators mayalso be connected with the pc-board. The pc-board is then, inparticular, inserted into the electronic housing and the electronichousing is sealed using a resin such that the pc-board is positivelyconnected with the electronics housing. Finally, the invention relatesto a hand-held power tool with an electric motor and a detachablebattery pack of the kind described above that can be locked togetherwith said motor and that drives the motor, whereby a device forestablishing the mechanical and electrical contact of the battery packwith a housing of the hand-held power tool is provided.

In the following, the invention shall be described in greater detailusing a drawing, whereby

FIG. 1 shows an exploded view of the electronics unit as well as thecorepack of a battery pack;

FIG. 2 shows a battery pack without battery housing, and

FIG. 3 shows a detail of FIG. 2 with regard to locking.

FIG. 1 shows an exploded view of a corepack (bottom image) which in itsentirety is designated with the number 12, as well as a pc-board 14 withsheet metal conductors 16 (center image) and an electronics housing 18(top image).

The corepack 12 comprises battery cells 20, whereby two cells 20′ and20″each are connected parallel to form one battery cell block. Thebattery cells 20 are lithium ion cells that, contrary to nickel cadmiumcells, allow for parallel connections. The battery cell blocks consistof the battery cells 20′ and 20″and are each connected in series. Thebattery cells 20 are supported by a cell carrier 22 and are separatedfrom each other by said cell carrier such that the battery cells 20 donot contact each other, which could lead to shorts. The poles of theindividual battery cells 20 are left open in the cell carrier 22 suchthat electrical contacting can be carried out.

In addition, a latching device 24 is provided at the cell carrier 22 andconsists of four pins that are provided with latches 26. The latches 26are slotted such that bouncing of the latch halves towards each otheroccurs in such a manner that the pins 24 including the latches 26 can beguided through an opening and then after rebounding a locking occursbehind the protrusion.

Later, during assembly, the electronics unit shown in the center imageis placed on the corepack 12. The electronics unit includes a pc-board14 that features various soldering points on its upper side 27 and alsoan electronic circuit that allows for loading a software. Additionalelectronics assemblies are located on the bottom side 28 of the pc-board14, for example light sources for a charge level indicator and switches,etc.

The sheet metal conductors 16 are connected with the pc-board 14 usingrivets 30 and have a material connection with the poles of the batterycells 20 via contact areas 32. Both the parallel and the seriesconnections among the individual battery cells are carried out using thesheet metal conductors 16. In addition, the sheet metal conductors 16provide a connection with the electronics via the rivets 30 that areused to attach the sheet metal conductors 16 to the pc-board 14. Aconnection of the cells 20 with the electronics using sheet metalconductors has the advantage that vibrations can be compensated becausethe sheet metal conductors 16 act as spring elements and in addition tothe electrical connection a mechanical connection between pc-board andbattery cells is established that locates the pc-board at the batterycells 20 after being welded to them.

In addition, the pc-board 14 exhibits recesses 34 that are located inthe area of the pin 24 and surround said pin.

Prior to the assembly, the pc-board 14 with the corepack is connected toan electronics housing 18, which is shown in the top image. For thispurpose, a sponge rubber element 36 is placed on the pc-board 14, andthe pc-board and the sponge rubber element 36 are then inserted into theelectronics housing 18. Thereafter, the electronics housing 18 is sealedwith a resin such that a solid connection between the pc-board 14 andthe electronics housing 18 is established.

A respective connection can be seen in FIG. 2, where the sealing of theelectronics components, for example the pc-board 14, etc. with theelectronics housing 18 has already been carried out. The sponge rubberelement 36 prevents the cast resin from entering the passage area 38.Later, loading of the software onto the pc-board is done via thispassage area 38.

Furthermore, both the pc-board 14 and the electronics housing 18 exhibita recess 40, or 42, respectively, in one corner area through whichcables 48 (ref. FIG. 2) can be routed from the bottom side of thepc-board 14 to the top side of the electronics housing 18. For thispurpose, the recess 42 of the electronics housing 18 exhibits a clamp 44that provides a guide for the cable 48. In the passage area 38, thecables 48 are then connected to a connection pin 50 and guided to theterminals 52, which later serve the purpose of establishing theelectrical contact with a hand-held power tool (FIG. 2).

In addition, FIG. 2 shows an already assembled battery pack, however,without a battery housing. In this case, the electronics unit comprisingthe electronics housing 18 as well as the no longer recognizablepc-board 14 have already been connected to the battery cells 20 bywelding. For further dampening, an additional dampening element 46 inthe form of a foam strip is placed between the housing and theelectronics housing prior to assembly.

Finally, a mechanical latching device for the battery pack with thehand-held power tool is provided using the housing.

FIG. 3 shows a detail, where the locking of the corepack 12 via the cellcarrier 22 and the slotted pin 24 to the electronics housing 18 can beseen. With regard to their positions, the pins 24 are designed such thatafter locking they do not protrude beyond the surface of the electronicshousing 18, or protrude only insignificantly.

Using the method described above, an electrical and mechanicalconnection between battery cells 20 to a pc-board can be realized in aparticularly simple manner. Through the electrical connection, it ispossible to determine the charge level of the individual battery cells20 or battery cell blocks through the voltage and use this informationto control the charging procedure. In addition, such an arrangementoffers the advantage of a reliable electrical connection of the batterycells 20 to each other and to the electronics as well as a vibrationstrength.

1. A battery pack, in particular one for a hand-held power tool,comprising at least two battery cells (20) and/or battery cell blocksconnected in series and an electronics unit with a printed circuit board(14), whereby sheet metal conductors (16) are provided for electricallyconnecting the in series connected battery cells (20) and/or batterycell blocks, characterized in that the sheet metal conductors (16) aredirectly connected to the pc-board (14).
 2. A battery pack as set forthin claim 1, characterized in that the sheet metal conductors (16) areconnected to the pc-board (14) both electrically and mechanically via aconnection element.
 3. A battery pack as set forth in claim 1,characterized in that the sheet metal conductors (16) are located at thepc-board (14) via rivet joints (30).
 4. A battery pack as set forth inclaim 1, characterized in that the battery cells (20) are lithium ioncells.
 5. A battery pack as set forth in claim 1, characterized in thattwo or more battery cells (20) are parallel connected into battery cellblocks.
 6. A battery pack as set forth in claim 1, characterized in thatthe sheet metal conductors (16) are connected to poles of the batterypacks (20) by welding or soldering.
 7. A battery pack as set forth inclaim 1, characterized in that the pc-board (14) together with theassembled sheet metal conductors (16) is housed in an electronicshousing (18) and in particular is embedded and sealed in it.
 8. Abattery pack as set forth in claim 1, characterized in that the batterycells (20) are supported and separated from each other in a cell carrier(22).
 9. A battery pack as set forth in claim 1, characterized in thatthe electronics housing (18) can be located on the cell carrier (22)using a latch connection.
 10. A hand-held power tool with an electricmotor and a detachable battery pack as set forth in claim 1 that can belocked together with said motor and that drives the motor, whereby adevice for establishing the mechanical and electrical contact of thebattery pack with a housing of the hand-held power tool is provided.